Two stroke engines are known which are not lubricated by mixing oil with the fuel but by supplying accurately metered quantities of oil to the bearings in the crankcase by means of a positive displacement pump. With such engines, if no oil is available for lubrication, then the engine can seize and be severely damaged. It is therefore important to ensure that the level of oil in the oil reservoir is monitored at all times and to give the vehicle driver ample warning of a depletion in the oil level.
To this end, it is known to provide two oil level warning lights, the first giving advance warning to replenish the oil reservoir and the second advising the driver to switch off the engine immediately to prevent it from being damaged.
There are several disadvantages in using a system with two different level sensors and lights. First, there is the cost arising from the duplication of sensors and lights. Second, the vehicle dashboard must be modified to accommodate an extra warning light, and an additional wire must be included in the wiring harness for this purpose. If a manufacturer is to offer a vehicle with a choice of two stroke and four stroke engines, this would require the different variants of the same model to have different electrical systems. Furthermore, two warning lights for the same liquid level may confuse the driver and may even suggest to the driver that the early warning light can be safely disregarded.